Dental casting apparatus.



1). s. MACKENZIE. I

DENTAL CASTING APPARATUS.

APPLICATION FILED 'mn, 1911.

1 0 9 0. L Patented Aug.19,19l3.

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DAVID STUART MACKENZIE, OF LEVIN, NEW ZEALAND.

DENTAL CASTING APPARATUS.

Specification of Letters Patent.

Patented Aug. 19,1 913.

Application filed May 4, 1911. Serial No. 625,007.

To all whom it may concern.

Be it known that I, DAVID STUART Mao- KENZIE, a citizen of the Dominionof New Zealand, and residing at Levin, in the Provincial District ofWellington, New Zealand,

have invented certain new and useful Imstructions, and method ofoperation, hereinafter set forth and claimed.

The drawing herewith is a sectional elevation of the apparatus.

'A casing 1 secured to a plate 2 has an air- The plate 2 is supportedupona base plate 4 by pillars 5 having eX- tensions 6 and nuts 7, thecover 3 being held by nuts 8. The casing contains anelectric muffle 9heated by a current of electricity derived from any suitable source ofsupply, and entering the casing and mufile by wires 10 and 11. Radiationof heat from the muffie is prevented by packing the. interior of thecasing around and above the muflle with asbestos 12.

A retort 13, made of fireclay or other refractory material, is adaptedto pass through a hole in the plate 2 and has an integral collar-14which is held airtight against the said plate by a cup-shaped presser 15having its rim bearing upon the collar 14. The retort 13 has adepression 16 to hold the metal to be melted and a passage or gate 17leads from the depression to the interior of the retort. The presser hasa hole in the bottom screw-threaded to screw upon the head 18 of a pipe19 communicating with a vacuum vessel 20. A holder 21 upon the presser15 enables the said presser to be screwed upon the head 18. Asbestoswashers 22 are provided. upon each side of the collar 14 for the purposeof making airtight joints.

A lock-nut 23 upon the head 18 has a handle 24, and makes an airtightjoint with the presser 15 by means of an asbestos washer 25. The pipe 19is provided with a stopcock 28, and the vacuum vessel 20 has a vacuumgage 29. To extract the retort. 13, the lock-uut23 is unscrewed andallowed to fall upon a tray 30 secured to the pipe 19. The presser 15 isthen screwed downward until it is free of the head 18, after which it isallowed to fall uponthe lock-nut 23 which is already resting upon theplate 30. The retort 13 can, then be readily withdrawn. A pipe 31provided with a stop-cock and a pressure gage 33 above the saidstop-cock connects a vessel 34 containing compressed air to the interiorof the muifle 9. The said vessel is provided with a pressure gage Avacuum in the vessel 20 is created by an air pump 36 which draws the airfrom the vessel 20 and delivers it into the vessel When the air in thevessel 20 becomes too attenuated for delivery into the vessel 3-1, a

stop-cock 37 is opened at the bottom of the pump to admit air from theatmosphere into the said pump 36. Communication between the vessel 20and the pump 36 is afforded by a pipe 38 furnished with a stop-cock 39,and a pipe 40 providedwith a cook 41 connects the pump to the vessel 34.The cocks 39 and 41 can be shut when a vacuum has been obtained in thevessel 20 and when pressure has been formed in the vessel 34.

The mold is prepared in the ordinarv way by filling the retort withinvestment material 44 wherein a mold 45 has been formed by a waxpattern or model. The retort is placed in position as shown in thedrawing with the material to be melted placed in the depression 16, andthe mufiie 9 heated ,by switching on the current of electricity by thewires 10 and 11.

A pyrometer of ordinary construction connected to wire 46 of platinum orthe like, indicates the temperature within the interior of the mullle 9,and when a temperature has been applied to the metal of sufficientheight and length of time to melt the metal in the depression 16, thecooks 2S and 32 are simultrmeously opened by turning a double ended key47 having end sockets 48 and 4.) fitting the spindles 50 and 51 of thecocks 32 and 28 respectively. The key 47 has an integral handle or lever52 whereby the key is rotated. The opening of the cock 28 creates avacuum in the investment 44- below the mold 45, and the opening of thecock 32 admits compressed air to the interior of the muille 9. Thesimultaneous opening of the cocks 28 and 32 causes the vacuum andcompressed air to be applied simultaneously. By making the admission ofthe pipe 511 at the bottom of the muille 9 the compressed air is heatedbefore it reaches the metal in the depression 16. The compressed air isalso previously heated in the vessel 34 by a lamp 54, or other source ofheat. 7 The gage 33 enables the air pressure in the muffle to beascertained when the cock 32 is closed, and a cock 55 in the pipe 31 andabove the gage 33, allows the compressed air to escape from the muflleprevious to the uncoupling, of the presser 15. The eftect'of using avacuum below and air pressure above the mold-1s that the castingsobtained are sound and free from blowholes throughout.

What I do claim and desire to secure by Letters Patent of the United-States is 1. A casting apparatus, comprising in combination, a casing, aretort extending into said casing and havi ga mold therein,

means in said casing for heating said retort, means for supplyingcompressed fluid to one side of the mold in said retort, a presseradapted .to be moved into and out of engagement with said retort, asupport for said presser, a passage through said support lead ing tosaid retort, and means for creating a reduced pressure in said passage.

2. A casting apparatus, comprising in combination. a casing, a retortextending into said casing and having a mold therein, means in saidcasing for heating said retort, means for supplying compressed fluid toone side of the mold in said retort, means for creating a reducedpressure on the other side thereof, and a presser adapted to be movedinto engagement with the outside of said retort, said presser'beingfirst moved longitudinally and then rotated to hold said retort inposition. I

3. A casting apparatus, comprising .in combination, a casing, a retortextending into said casing and having a mold therein, means in saidcasing for heating said retort, means for supplying compressed fluid toone side of the mold in said retort, means for creating a reducedpressure on the other side thereof, a presser adapted to be moved intoengagement with the outside of said retort,

screw-threads formed on said presser, and a screw-threaded member forsupporting'said' presser, the presser being normally out of engagement\vith'said screw-threaded member, but being movable longitudinally toengage said screw-threads and then rotatable to firmly hold said retortin position.

4. A casting apparatus, comprising in combination a casing, a retortextending into said easing and having a mold therein, means in said.casingfor heati'ng said retort, means for supplying compressed fluid toone side of the mo in said retort, a,hollow presser enga ng the outsideof said retort for holding it in position in said casing, an opening insaid retort communicating with said hollow presser, means for creating avacuum in said presser and means for moving said presser into and out ofengagement with said retort.

5. A casting apparatus comprising in combination a casing, a retortextending into ,said casing and having a mold therein,

meansin said casing for heating said retort, means for supplyingcompressed fluid to one side ofthe mold in said retort, a hollow presserengaging the outside of said retort for holding it in position in saidcasing, an opening in said retort communicating with said presser, ascrew-threaded portion on said presser, a screw-threaded member engagingtherewith, a hollow support for said screw-threaded member,communicating therethrough with said hollow presser, means connected tosaid hollow support for producing a vacuum in the hollow presser andmeans for causing relative rotary .motion between the presser andscrew-threaded member for moving said presser into and out of engagementwith said retort.

6. A casting apparatus, comprising in combination a casing, a retortextending into said casing and having a mold therein, a space in saidcasing communicating with one side, of the mold in said retort, a pipefor'supplyi'ng compressed fluid'to said space,

in said presser, a valve in each of said pipes,

a bar having means at each end for engaging the stems of said valves,and means for operating said bar to simultaneously open or close saidvalves. 10

, 7. A casting apparatus, comprising in combination a retort extendinginto said casing and having a mold therein, an electric muflle in saidcasing for heating said retort, means for supplying compressed fluid toone side ofthe mold in the retort, means for oreating a vacuum on theother side thereof, a flange formed on said retort engaging the outsideof said; casing, a presser engaging said flange for holding the'retortin position in said casing, washers arranged between said flange andcasing and presser for forming -fluid,tight joints and, means for movingsaid presser into and out' of engagement with said flange.

8. A casting apparatus, comprising in combination a casing, a retortextending into said casing and having a mold therein, an

electric mufile in said casing for heating said retort, a space in saidcasing between said muflie and retort, a pipe for supplyingcompressedfluid to said space, a hollow presser engaging the outside of saidretort for holding it in position in said casing, an opening in saidretort communicating with said presser, a screw-threaded portion on saidpresser, a screw-threaded member engaglng therewith,- a hollow supportfor said member, means connected therewith for producing a vacuum insaid presser, a screw-threaded locking member Working on saidscrewtlneaded member and engaging said. presser, handles connected tosaid presser and locking member for rotating them, a tray carried bysaid hollow support, valves in said means at each end thereof to engagethe stems of said valves and a handle extending from said bar forrotating it to simultaneously open and close said valves.

In testimony whereof I have signed my name to this specification in thepresence of two Witnesses.

' DAVID STUART MACKENZIE.

Witnesses:

ERNEST SMITH BALDWIN, ANNIE DOROTHY MCKENZIE.

